Mechanical property testing machine

ABSTRACT

In accordance with the present invention, a low in weight, portable, mechanical property testing machine is provided in which no special testing machine foundation is required, and a standard power supply may be used. The applied load to test the specimen is applied by the action of a rod making a single stroke within a cylinder containing hydraulic fluid. The inside diameter of the cylinder is significantly greater than the diameter of the rod. The hydraulic fluid transmitted from the cylinder is substantially ripple free and applies an even load to the specimen being tested through a second fluid cylinder and piston acting therein. The use of valves, as used in the prior art may thus be avoided, thus achieving simplicity of operation. To absorb the shock created by the specimen breaking, a dash pot is provided out board of the second piston as a shock absorber. When the specimen being tested is a threaded fastener, the fastener is gripped by a collet made of two threaded and tapered longitudinally split, pieces held together with a spring. As a load is applied to the specimen, the two collet pieces are locked together by the tapers, assuring thread alignment. The split collar also preferably has different threads per inch at each end of the collet pieces to adapt to different threads of different specimens. Split collars of different geometry are used to test thin, non-threaded specimens.

BACKGROUND OF THE INVENTION

In U.S. Pat. No. 2,001,711 a portable tensile testing machine isdisclosed which is operated through a fluid cylinder which is operatedby a rack and pinion pump shown in FIG. 5, and a valve system shown inFIG. 6. The separate rod, the dash pot and the alignment collet does notappear to be shown.

U.S. Pat. No. 2,321,875 discloses the use of a single fluid cylinder ina tensile testing machine. The separate supply chamber, and rod operabletherein, and dash pot, do not appear to be disclosed.

U.S. Pat. No. 3,329,010 discloses a tensile testing machine for fabrics.A fluid operating cylinder is used to apply the tensile force. Theseparate supply cylinder, the alignment collet, and the dash pot do notappear to be disclosed.

U.S Pat. No. 3,407,651 discloses a tensile testing machine in which thetensile load is applied at a high rate of speed by an explosive chargewhich severs a frangible member shown in FIG. 2. The collet alignmentfeature, and the single stroke of a hydraulic ram are not apparentlydisclosed. A dash shock absorber appears to be shown in FIG. 1 at 37.

U.S. Pat. No. 3,548,646 discloses a tensile testing assembly operated byhigh pressure gas applied to both sides of piston 15. The end ofspecimen 21 is located by co-operating tapers on the slot in piston 15,and an adjustable set screw. The single stroke hydraulic supply ram doesnot appear to be disclosed.

U.S. Pat. No. 3,934,464 discloses a pipe ring testing apparatusincluding a manually operated pump 40 and a tensile drive cylinder 16controlled by valve 38. The specimens are semi-circular shoe discs. Therod-in-chamber, collet alignment feature, and the dash pot, do notappear to be shown.

SUMMARY OF THE INVENTION

A. Objects

One object of the present invention is to provide a testing machinewhich is light in weight and portable.

Another object of the invention is to provide a testing machine whichcan utilize a standard power supply.

Another object of the present invention is to provide a testing machinewhich is simple in operation.

Another object of the present invention is to provide a testing machinein which the machine is operated by a single stroke of a rod operatingin a fluid cylinder.

Another object of the invention is to provide a testing machine in whichalignment of the specimen in the machine is provided.

Another object of the invention is to provide a testing machine whichuses a single adapter for both load and elongation testing.

Another object of the invention is to provide a collet design which isadaptable to different size threads.

Another object is to provide a cushion for any forces resulting from thespecimen severing.

Another object is to provide a testing machine in which the applied loadis continuously readable.

Another object of the invention is to provide a testing machine in whichthe entire stress strain curve may be determined and or/printed out.

Another object is to provide a testing machine in which tests cannot bemade unless a protective cover is latched in place prior to the start ofthe test.

B. Summary

In accordance with the present invention, a low in weight, portable,mechanical property testing machine is provided in which no specialtesting machine foundation is required, and a standard power supply maybe used. The applied load to test the specimen is applied by the actionof a rod making a single stroke within a cylinder containing hydraulicfluid. The inside diameter of the cylinder is significantly greater thanthe diameter of the rod. The hydraulic fluid transmitted from thecylinder is substantially ripple free and applies an even load to thespecimen being tested through a second fluid cylinder and piston actingtherein. The use of valves, as used in the prior art may thus beavoided, thus achieving simplicity of operation. To absorb the shockcreated by the specimen breaking, a dash pot is provided out board ofthe second piston as a shock absorber. When the specimen being tested isa threaded fastener, the fastener is gripped by a collet made of twothreaded and tapered longitudinally split, pieces held together with aspring. As a load is applied to the specimen, the two collet pieces arelocked together by the tapers, assuring thread alignment. The splitcollar also preferably has different threads per inch at each end of thecollet pieces to adapt to different threads of different specimens.Split collars of different geometry are used to test thin, non-threadedspecimens. In a preferred embodiment, a reversible washer in which afirst face is used to hold the fastener in place and in alignment in afirst test, is also used to test the elongation of the fastener in aseparate test, through the use of a second, tapered face. The load usedin a given test is preferably continuously readable from a digitalprocess controller which determines the applied load from the hydraulicpressure applied to the operating cylinder. The machine may also be usedto determine the complete stress-strain curve for the specimen bycomputer print-out. The digital process controller will also storepertinent test information, and print out the information for review. Asa safety feature, no tests can be run unless a safety cover is latchedin place, which covers the testing apparatus. Specimens may be tested intension, compression, and shear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of the mechanical property testingmachine of the present invention.

FIG. 2 is a detail view of the tension carrier illustrating the housingportion and the two piece collet.

FIG. 3 is a detail view of the power cylinder, power piston, and dashpot used in the mechanical property testing machine of the presentinvention.

FIG. 4 is a view of the reversible washer of the present invention.

FIG. 4a is a side elevation view of FIG. 4.

FIG. 4b is an end view of FIG. 4a.

FIG. 5 is an end view of the use of the reversible washer.

FIG. 5A is a view of the use of the tapered face of the reversiblewasher as used in the testing machine of the present invention.

FIG. 6 is a graph of time against load resulting from the hydraulicsupply unit.

FIG. 7 is a vertical sectional view of an embodiment of the inventiondirected to a compression testing machine.

FIG. 8 is a sectional view looking in the direction of the arrows alongthe line 8--8 in FIG. 1.

FIG. 9 is a sectional view of another compression testing embodiment ofthe present invention. FIG. 10 is an end view of FIG. 9.

FIG. 11 is a sectional view of a shear test embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The mechanical property testing machine of the present invention isindicated in the drawings at 10. The machine includes a hydraulic supplyunit 12, and a testing unit 14 Preferably, both units are provided in asingle contained housing which is light-weight, and portable, and whichcan readily be connected to existing power supplies, such as 110 Voltelectricity, and/or conventional shop air pressure. No special testingmachine foundation is required.

The supply unit includes a first fluid cylinder 16 having a rod 18operable therein. The rod 18 extends through a packing 20, and a pair of"O" ring seals 22, and 24, which are located within a bore 26 in thecylinder 16. The rod 18 is of considerably smaller diameter than theinside diameter of cylinder 16.

The rod 18 is connected to a drive means 28. The drive means maycomprise a rack and pinion, a nut and screw gear, an air cylinder, oranother hydraulic cylinder. In the embodiment illustrated the drivemeans comprises a rack 30 connected at one end 32 to the outer end 34 ofthe piston 18 with a threaded fitting 36. The pinion 38 has teeth 40which engage the teeth 42 on the rack 30.

The pinion 38 is mounted upon a rotatable shaft 44, driven by anappropriate power source, illustrated as an electric motor 45, aninternal combustion engine, or another fluid cylinder. An importantfeature of the present invention is that it can be powered by readilyavailable power sources, such as a 110, or 240 Volt electric motor, aconventional, low horse-power internal combustion engine, orconventional shop air.

FIG. 6 illustrates a plot of time of application of the rod into thecylinder 16 against resulting force which occurs from displacement ofthe rod within the cylinder. It is apparent that in portion A of thecurve, the amount of load generated with time is relatively small.However, after the point B is reached a different rate of change ofapplied load with time occurs so that in the section C a great deal ofapplied load results from a small change in time. It is apparent thatwith the supply system of the present invention after the initial timeperiod labeled A in FIG. 6 has transpired, a great deal of applied loadresults from a further movement of the piston as time progresses.

The cylinder 16 includes a threaded opening 46 which receives a threadedfitting 48 of a flexible hose 50. Flexible hose 50 carries hydraulicfluid from the cylinder 16 to the testing unit 14, and through a line150 to a digital process controller 152.

Testing unit 14 includes a frame structure 60, including laterallyspaced blocks 62, and 64. Elongated tie rods 66 extend between theblocks. Fasteners 70 hold the tie rods in place in block 62, and theends 68 of the tie rods are threaded into threaded openings 72 in block64.

Block 62 includes a bore 74 which defines a shoulder 76. A washer 78 ofappropriate diameter is provided whereby a test specimen 80 having ahead 81 will be held in place within block 62 of the testing unit 14. Ina preferred embodiment of the invention the washer 78 is reversible,including a first face 78a shown in FIG. 4, for use in conventionaldirect alignment mechanical property testing, and a second face 78b foruse in testing specimens requiring an elongation test according to ASTMSpecification 5.52 (copy in application file). FIGS. 5 and 5A show thespecimen mounted in place with tapered face 78b to make an elongationtest in which the specimen rotates as the load is applied until thespecimen severs. In either test, the specimen 80 is threaded at itsinner end 82. The threaded inner end extends into a slot 95 in the bodyportion 94 of load carrier 92 (FIG. 2).

End 82 is threaded unto a two piece collet generally indicated at 83,including a pair of collet pieces 84 and 85. The pieces are cylindricalin shape and include respective outer tapered portions 86, 86a; and 87,87a. The pieces are preferably threaded with different internal,standard threads at each end 88, and 89. The halves are essentiallymirror images of each other, and are split along a longitudinalcenterline, C.L. An "O" ring 90 is located in a slots 91, and 91a,respectively which extend around the two collet halves 84, and 85. Thetest specimen is threaded into both halves, according to the particulartype of thread the specimen has and the "O" ring surrounds the halvesand holds the assembly together when a test is to be made. The taperedcollet edges 86, 86a; and 87, 87a; correspond to the taper 96 in theslot 95.

When a specimen is placed in the collet pieces and load carrier 92 inthis manner, proper alignment for the test is assured. Furthermore, whenthe specimen breaks during the test, the portion of the broken fasteneris readily removed because the collet pieces are longitudinally split.

Block 64 includes a bore 100 having a shoulder 101 into which extends athreaded extension 98 of load carrier 90. A packing 102 is provided inbore 100. A piston 110 includes a slot 112 to receive an "O" ring 114.Piston 110 includes a body portion 116 which is of larger diameter thanload carrier extension 98. Hydraulic fluid supplied from the singlestroke of rod 18 enters through fitting 104 and drives piston 110 fromleft to right in FIG. 1 to apply tension to specimen 80 through tensioncarrier 92.

The fitting 104 connected at the opposite end of flexible tube 50extends into threaded port 106 to supply hydraulic fluid to secondoperating cylinder 108. Another flexible hose 150 extends to digitalprocess controller 152.

Piston 110 essentially floats on load carrier extension 98 because ofits greater diameter. A load carrier nut 118 is threaded unto loadcarrier extension 98, and includes a piston head 120 located adjacentpiston head 110. Piston 110 is trapped between piston head 120, and theshoulder 101 in cylinder 64. A groove 122 in piston head 120 receives an"O" ring 124. A plate 126 having a round center opening 128 is held uponblock 64 with fasteners 130 and defines with block 64 a dash pot chamber131.

A vent opening 132 with a carefully sized cross section 134 is providedin block 64. Another "O" ring 136 is provided in a groove 137 in plate126 to seal dash pot chamber 130.

After the fluid pressure applied into cylinder 108 causes piston 110 tomove from left to right in FIG. 1, with sufficient force to breakspecimen 80, the dash pot chamber 130 cushions movement of tensioncarrier 90 as air exits vent 132 and small cross section 134.

A handle 140 including a body portion or hub 142 is attached to carriernut 118 with fasteners 144, and is threaded at 146 to engage loadcarrier extension 98. The arms 148 extending radially outwardly from thebody portion or hub 142 facilitate locating load carrier nut 118, piston120, and piston 110 in the proper location within block 64. Since piston110 is movable with respect to load carrier extension 98, this allowsdifferent length fasteners to be tested, and also locates piston 110within block 64.

Digital process controller 152 is a commercially available load readingdevice which is computer controlled. The applied load is continuousreadable from the unit. The unit also stores mechanical property datasuch as tensile strength, compressive strength, elongation, andreduction in area. One or more of these parameters can be continuous,read and/or plotted by the controller. The entire stress strain curvemay be plotted for a test if desired. As an example an Eaton QualitySignature Q5-200 may be used. Additional information may be obtainedfrom Eaton Corp; Automation Products Div.; 901 S. 12th St., Watertown,WI; 53094. The applied load, and the stress-strain data may also beobtained with a strain gauge S.G. in FIG. 2 supplying the data throughleads shown dotted. Cover 160 is pivotable mounted on unit 14, on block14 at 162. The cover includes a body portion 164 and a distal end 166having a catch 168 which engages a latch 169. Latch 169 controls anelectrical switch 170. Switch 170 controls the electrical circuit tomotor 45 and computer controller 152. These units will not be connectedif cover 160 is not latched in place.

In operation, to test a specimen, a washer 78 of the proper diameterwith face 78a is selected to hold specimen head 81 in place. Handle 140is used to move piston 110 and load carrier nut 130 to the properlocation for this specimen in cylinder 108. The threaded end 82 ofspecimen is then threaded into both pieces 84 and 85 of the collet 83,with the hollow ring 90 located around the collet pieces. With cover 160closed electric motor 45 is used to rotate shaft 44 and pinion 38. Thismoves rack 30 and rod 18 from left to right in FIG. 1, and in a singlestroke forces sufficient hydraulic fluid from cylinder 16 throughfitting 48 and flexible tube 50 into chamber 108 to move piston 110 fromleft to right in FIG. 1, to first move tapers 86a and 87a intoengagement with load carrier taper 96 to achieve proper specimenalignment. This applies sufficient tensile force to sever specimen 80.When the specimen is severed the force is applied into dash pot 130 byload carrier nut piston 120, causing air to exit slowly throughcontrolled vent section 134. This cushions the load carrier assembly.The severed specimen is easily removed with head 81 and collet portions83 and 84. The stress-strain curve and other relevant data from processcontroller 152 may be printed out. If desired, an elongation test maythen be made with the adapter face 78b holding the specimen in place asshown in FIG. 5A, and additional test data and specimen severingstrength under this load condition obtained.

As mentioned above, a strain gauge S.G. in FIG. 2 located in a groove inpiston 120, having electrical leads shown dotted in FIG. 2 may also beused to supply the data to the process controller 152. A differentprocess controller than the specific one mentioned above should be usedwhich reads electrical stress-strain data instead of one that readspressure.

Another embodiment of the present invention is shown in FIG. 7. In thisembodiment a compression testing machine 200 includes a cylinder 202having a piston 204 movable back and forth therein which has a pistonhead 206 and a groove 208 which receives an "O" ring seal 210. Cylinder202 includes a transverse member 212 having an opening 214 and a groove216 which receives an "O" ring 218 which seals piston 204.

Piston 204 includes an opening 220 which receives a threaded collet 222which receives a threaded end 224 of a compression test specimen 226.The opposite end of specimen 226 is held in place upon a compressiontest mounting block 230. A flexible conduit 50' carrying hydraulic fluidfrom cylinder 16 is connected to a fitting 232.

In operation, a single stroke of rod 18 in cylinder 16 causes hydraulicfluid to enter cylinder 202 and move piston 204 such as to apply acompressive load to specimen 220. The applied load and other parametersmay be read out by digital process controller 152, including compressivestrength elongation in compression, etc.

It is apparent from FIG. 7 that the supply cylinder 16 and rod 18 may beused to supply an applied load to a compression test as well as atensile test.

The supply cylinder 16, and rod 18 may also supply an applied load to ashear test by pulling or pushing one portion of a shear test specimen,with respect to another portion of the specimen. This is described ingreater detail in connection with FIG. 11, hereinafter.

Another embodiment of the invention is shown in FIGS. 9 and 10. In thisembodiment another compression testing unit 250 includes a test frame252 having an opening 254 which receives a stationary compressionfixture 256 including a bolt 260 having a threaded end 262 held placewith a nut 264. Fixture 256 further includes a plate 266 with openings268 which receive tie rods 270 held in place with fastener nuts 272.

Rods 270 extend through openings 274 in a movable compression fixture276 including plates 278 and 280 and tie rods 282 extending therebetweenheld in place, respectively with fasteners 284 and 286. Rods 270 extendto a plate 288 inside movable fixture 276, and are held in place withfasteners 290. A specimen 292 for testing is located between plates 278and 288.

A load carrier 294 includes a shaft portion 296 which extends up toplate 280 and is welded thereto with a weld 298.

In operation, specimen 292 is tested in compression by a compressiveload applied to load carrier 294 by a suitable means such as movement ofhydraulic fluid form cylinder 16 by the action of rod 18 into cylinder108. Movable fixture 276 moves from right to left in FIG. 9 untilsufficient compressive load is applied to specimen 292 to sever the samein compression. Preferably the applied load is read out on digitalprocess controller 152, and the resulting load is cushioned by dash pot130.

Another embodiment of the invention is shown in FIG. 11. In thisembodiment a shear test fixture is shown at 300. In this embodiment, afixture frame 302 includes an opening 304 which receives a stationaryshear fixture 306. Stationary fixture 306 includes a bifurcated rod 308which is threaded at its outer end 310 and receives a nut 312 to hold itin place within the frame 302.

Bifurcated rod 308 includes a body portion 314, and legs 316 and 318which have respective openings 320, and 322, which receive a shearspecimen 324 having a head 326, a shank portion 328, and a threadeddistal end 330. A load carrier 332 including a body portion 334, a head336, and a specimen engaging portion 338, and a specimen receivingopening 340 is provided.

In operation, with a specimen 324 in place as shown in FIG. 11, asuitable force, such as hydraulic fluid from cylinder 16 actuated by rod18 transferred into to cylinder 108 causes load carrier 332 to move fromright to left in FIG. 11, which applies a shear load to specimen 324.The applied shear load may be read out on digital process controller152. When the specimen shears, if the load is applied with enough forceto sever the specimen, the resulting severing load is preferablycushioned by dash pot 130.

It is thus apparent that the mechanical property testing machine of thepresent invention may be used to test specimens loaded in tension,compression, and shear.

What is claimed is:
 1. An improved mechanical property testing machinecomprising:means for supporting a specimen to be tested; carrying meansfor applying a test load including a specimen testing cylinder, and atest piston moveable therein to apply a test load to the specimen; asupply hydraulic cylinder; a rod moveable therein having an outsidediameter significantly less than said supply cylinder; power means forapplying a force to said rod of sufficient force whereby with a singlestroke of said rod, hydraulic fluid is conveyed to said test cylinderwhereby a test load is applied to said specimen; means for obtainingalignment between said specimen and said carrier comprising amulti-piece collet which is split longitudinally which threadablyengages said pieces; and a resilient member surrounding said colletpieces to hold the assembly together.
 2. An improved testing machineaccording to claim 1 wherein the cushioning means comprises a dash potlocated outboard of said test piston.
 3. An improved testing machineaccording to claim 1 wherein the specimen and collet pieces are receivedwithin a tapered opening in said carrier and wherein the collet piecesinclude tapers which engage the taper on said carrier, and wherein saidcollet pieces are threaded with different threads at each end.
 4. Animproved mechanical property testing machine comprising:means forsupporting a specimen to be tested; carrying means for applying a testload including a specimen testing cylinder, and a test piston movabletherein to apply a test load to the specimen; means for obtainingalignment between said specimen and said carrying means; a supplyhydraulic cylinder; a rod movable therein having an outside diametersignificantly less than said supply cylinder; means for applying a forceto said rod of sufficient force whereby with a single stroke of saidrod, hydraulic fluid is conveyed to said test cylinder, whereby a testload is applied to said specimen; conduit means for supplying sufficienthydraulic fluid to said cylinder to sever said specimen; means forcushioning the force resulting from severing the specimen comprising adash pot located outboard of said test piston; and wherein said testcylinder and said dash pot are located adjacent each other.
 5. Animproved testing machine according to claim 4 wherein said rod is drivenby a rack attached to the outer end of said supply piston, and a pinionwhich engages said rack.
 6. An improved mechanical property testingmachine according to claim 4 wherein the machine is connected to adigital process controller which continuously reads a desired parameterand stores data for calculating other parameters.
 7. An improvedmechanical property testing machine according to claim 6 wherein anapplied load is printed out by the digital process controller.
 8. Animproved mechanical property testing machine according to claim 7wherein a stress strain curve is plotted out by the digital processcontroller.
 9. An improved mechanical property testing machine accordingto claim 4 wherein the mechanical property tested is a tensile load andwherein the properties measured are tensile properties.
 10. An improvedmechanical property testing machine according to claim 4 wherein thetest load is applied to compress a specimen and wherein compressivemechanical properties are measured.
 11. An improved mechanical propertytesting machine according to claim 4 wherein the applied load is appliedto shear a specimen, and shear mechanical properties are measured. 12.An improved load testing machine comprising:means for locating aspecimen to be tested in said machine; a power cylinder for receivinghydraulic fluid and a power piston to apply a testing load to saidspecimen; means for applying hydraulic fluid to said power cylinder todisplace said piston; a dash pot located outboard of said power pistonto cushion any forces resulting from severing said specimen; and whereinthe piston head for the test cylinder is located adjacent the pistonhead for the dash pot.
 13. An improved load testing machinecomprising:means for locating a specimen to be tested in said machine; atest cylinder for receiving hydraulic fluid and a test piston to apply atensile load to said specimen; means for applying hydraulic fluid tosaid test cylinder to displace said test piston; a dash pot locatedoutboard of said test piston to cushion any forces resulting fromsevering said specimen; wherein the piston head for the test cylinder islocated adjacent the piston head for the dash pot, and is movable backand forth by said dash pot piston.
 14. An improved mechanical propertytesting machine comprising:means for supporting a specimen to be tested;carrying means for applying a test load including a specimen testingcylinder, and a test piston movable therein to apply a test load to thespecimen; a supply hydraulic cylinder; a rod movable therein having anoutside diameter significantly less than said supply cylinder; means forapplying a force to said rod of sufficient force whereby with a singlestroke of said rod hydraulic fluid is conveyed to said test cylinderwhereby a test load is applied to said specimen; and including safetymeans to prevent operating of the machine unless the safety means are inthe safe operation position.
 15. An improved mechanical property testingmachine comprising:means for supporting a specimen to be tested;carrying means for applying a test load including a specimen testingcylinder, and a test piston movable therein to apply a test load to thespecimen; means for obtaining alignment between said specimen and saidcarrying means; a supply hydraulic cylinder; a rod movable thereinhaving an outside diameter significantly less than said supply cylinder;means for applying a force to said rod of sufficient force whereby witha single stroke of said rod, hydraulic fluid is conveyed to said testcylinder, whereby a test load is applied to said specimen; conduit meansfor supplying sufficient hydraulic fluid to said cylinder to sever saidspecimen; means for cushioning the force resulting from severing thespecimen comprising a dash pot located outboard of said test piston;said test cylinder and said dash pot located adjacent each other; andsaid carrier including a threaded extension, and wherein said specimenis held in place with a reversible adapter for mechanical propertytesting.
 16. An improved load testing machine comprising:means forlocating a specimen to be tested in said machine; a power cylinder forreceiving hydraulic fluid and a power piston to apply a testing load tosaid specimen; means for applying hydraulic fluid to said power cylinderto displace said piston; a dash pot located outboard of said powerpiston to cushion any forces resulting from severing said specimen; thepiston head for the power cylinder being located adjacent the pistonhead for the dash pot; and wherein the weight of the machine does notexceed about 300 pounds, and is therefore portable.
 17. An improvedmechanical property testing machine according to claim 16 wherein themachine is operable by readily available standard power source.
 18. Animproved mechanical property testing machine according to claim 17wherein the readily available power source is 110 volt electricity. 19.An improved mechanical property testing machine according to claim 17wherein the readily available power source is ordinary shop air.
 20. Animproved mechanical property testing machine comprising:means forsupporting a specimen to be tested; carrying means for applying a testload including a specimen testing cylinder, and a test piston movabletherein to apply a test load to the specimen; a supply hydrauliccylinder; a rod movable therein having an outside diameter significantlyless than said supply cylinder; means for applying a force to said rodof sufficient force whereby with a single stroke of said rod hydraulicfluid is conveyed to said test cylinder whereby a test load is appliedto said specimen; including safety means to prevent operating of themachine unless the safety means are in the safe operation position; andwherein safety means include an electrical switch which preventsoperation of the machine unless the machine is in the safe position.